Various forms of conductive or dielectric material gauges have been provided in the prior art in which a work piece is used to influence the reactance of a coil or capacitance to alter the circuit parameters of a resonant circuit or bridge with the electrical changes caused by this influence measured as an indication of some parameter or characteristic of the part. These prior art circuits have included the use of two oscillators with the measurement made with respect to the beat frequency therebetween which varies aas the resonant frequency of one or the other of the oscillators is influenced by the presence of a test part. While these prior art guages have been useful in certain applications there remains a need for a guaging circuit in which a wide range of measurement can be made with selected sensitivity, particularly in being able to provide a stable system in which minute deviations among tested work pieces can be detected. It is particularly desirable that such measurements be accomplished with ease by unskilled personnel working in a manufacturing or production environment where stability and reliability under relatively adverse operating conditions are of paramount importance.